Abstract: A method is described for improving the oxidation durability of overlay coatings. By polishing the surface to reduce the surface roughness to less than about 15 microinches AA the initial oxidation durability of the material, the point at which oxide spallation is first observed, can be increased from about 5 hours to about 200-300 hours.

Abstract: Disclosed is a two-step process of joining a lead wire to a 2.times.10.sup.-6 m thick platinum alloy film which rests upon an equally thin alumina insulating layer which is adhered to a metal substrate. Typically the platinum alloy film forms part of a thermocouple for measuring the surface temperature of a gas turbine airfoil. In the first step the lead wire is deformed 30-60% at room temperature while the characteristic 10.sup.6 ohm resistance of the alumina insulating layer is monitored for degradation. In the second step the cold pressed assembly is heated at 865.degree.-1025.degree. C. for 4-75 hr in air. During the heating step any degradation of insulating layer resistance may be reversed, provided the resistance was not decreased below 100 ohm in the cold pressing.